I've been following this one from the beginning, not sure you can describe it as up and coming as he's been working on it for a number of years

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Synekism is an attempt at a modern city simulator rooted in procedurally generated content. The project was started in 2010 to address some frustrations with the city simulation video game genre. It is actively developed on and currently in a purely alpha-experimental stage. Updates on the project are posted on the first of every month. Note that work on this project is more or less done by one person so progress will be slow, but steady.